Heated or refrigerated dispensers for delivering liquid or semi-liquid food products are commonly used in foodservice restaurants, catering, convenience stores and other commercial or public food establishments. The known dispensers are usually adapted for receiving food bags in a housing and to deliver the food by using pumps and/or gravity forces to a dispensing area.
Certain food product, such as cheese sauces and the like, usually requires to be served at warm temperature to adapt to culinary habits and/or to improve the digestion of fat. Other food products are adapted to be stored at ambient such as UHT cream, sterilized salad dressing or pudding but are desirable to be served at a refrigerated state. These food products are also usually low acid food which may be easily subjected to bacterial spoilage when opened, whereby heating or cooling permits storing the food in safer bacteriological conditions. The products usually need to be stored in aseptically hermetic flexible packages such as pouches, which are opened at the time the product is dispensed. Traditionally, the pouches are usually of relatively large size, in general of several kilograms, thus requiring a relatively long time before obtaining a controlled hot/cool temperature acceptable for serving.
One disadvantage of having a long heat-up/cooling-down time is that a fully warm/cool food bag may not be rapidly available when the demand for food exceeds the warming/cooling operation time for the new bag. Another disadvantage is when the bag is opened before the product reaches a sufficiently safe temperature level, i.e., about 60° C. in the case of hot product or below 4–6° C. for refrigerated products, the risk of bacterial contamination or spoilage seriously increases.
For instance, the American NSF standards require that potential hazardous food products having a pH level of 4.6 or less be rethermalized, i.e., heated from refrigerated or ambient state to an elevated temperature of not less than 140° F., must be capable of heating the food product to that temperature within four hours. For example, by using existing commercial equipment, the average heat-up time for large size pouches is more than 2 hours, most often more than 5 hours and sometimes more than 10 hours before the center part of the pouch can reach an acceptable warm temperature of 60° C. from ambient.
In order to meet with the regulations, prior solutions consisted of pre-warming the bag in a hot water bath or in microwave oven, then transferring the preheated bag to the dispensing unit where the bag remains temperature controlled. However, this is not satisfactory as it requires an additional piece of equipment for heating available. A water bath is usually cumbersome and requires a long time to warm up. Microwave heating also suffers from non-homogeneous heating problems with formation of cold and hot spots in the food. It also requires manipulation and surveillance by the foodservice operators to transfer the food pouch from the microwave unit to the holding unit. Finally, it is required to invest in microwave ovens of sufficiently large capacity and of wide radiation fields to accommodate large size pouches.
Similarly, for sterilized food products that are desirable to be served refrigerated, it is frequent that the foodservice operator cannot count on a refrigerating room for pre-cooling the food due to lack of space or for economical reasons.
U.S. Pat. No. 5,803,317 to Wheeler relates to a heated dispensing apparatus for dispensing products at an elevated temperature which allows packaging of the product in a container, such as a flexible bag, with a discharge tube extending therefrom. The dispenser includes a receptacle with an outlet opening in the lower portion thereof and a pump adjacent to the outlet opening. A heater is provided for heating the food bag in the receptacle and the discharge tube passing through the pump and maintaining both the bag and the tube at a desired elevated temperature. The receptacle is arranged to accommodate the reception of so-called “bag-in-box” type of package as illustrated in FIG. 1 of the patent. This type of package is disclosed in U.S. Pat. Nos. 3,173,579 and 4,796,788. The box portion of the “bag-in-box” type package is not required for use with the dispensing device. The bag itself is usually a bulky flexible bag with a fitment protruding on one side of the bag. The bag is arranged in the receptacle so that only the side with the fitment is positioned adjacent to a sloped heated bottom wall of the receptacle with the fitment of the bag passing through the outlet opening which ends or extends by a discharge tube. Due to the position of the bag in the receptacle, the thermal transfer from the receptacle to the bag remains relatively poor, thereby leading to excessive heat-up time when cold and large size bags are loaded for rethermalization. Furthermore, the heating pattern cannot be obtained uniformly within the product and a heat gradient is likely to form with the warmer side in contact with the receptacle and the colder side opposite. As a result, the food product may experience browning and darker spots, which consequently affect the quality and shorten the shelf life of the food product.
U.S. Pat. No. 6,003,733 to Wheeler notices the heating of the food product by pure conduction transfer as taught by U.S. Pat. No. 5,803,317 does not always provide an optimal uniform heating and may make the internal and external receptacle surfaces extremely hot thereby increasing the difficulty of handling the dispenser. Therefore, it proposes to replace the conduction means by convection heating means using a rear heating assembly to continuously circulate heated air into the internal cavity around the receptacle for the bag to maintain the food product at elevated temperature. However, the time necessary for heating a large capacity bag from ambient to a temperature of serving remains a significant problem with such a device as well. A heating gradient is also likely to occur as the bag presents both heat sink zones and air contact zones of large surfaces due both to the type of bag and to the manner the bag rests in the receptacle.
U.S. Pat. No. 6,016,935 relates to a viscous food dispensing arid heating/cooling assembly which is adapted to receive large food reservoirs of the “bag-in-box” type in a manner similar to the previous patent references; the improvement consisting in a specific air flow circulation to heat both the reservoir and the discharge tube.
U.S. Pat. No. 6,056,157 to Gehl proposed a dispensing unit with a heated hopper which is sized to receive two superposed “bag-in-box” type bags: a lower dispensing food bag resting flat along a bottom sloped wall with its fitment oriented horizontally and operatively connected to a dispensing unit and a second bag placed on top of the lower bag to serve as a weight for promoting gravity flow from the lower dispensing food bag and to precondition the second food bag. Due to the relatively thick material mass created by the superposition of two bulky bags, the time for heating the bag is very long. Similarly, more thermal energy is required for constantly maintaining the bags at warm temperature. The food will also experience a heat gradient with quick apparition of brown and dark spots. In this prior art device, a preheating compartment may be provided in the hopper to preheat a food bag more rapidly. The dispensing bag can then spread out in the hopper below the preheating compartment for dispensing purpose. The manner the bag spreads out in the hopper is similar to the previously discussed patents. Such heating and dispensing configuration has several shortcomings. Firstly, the heating of the dispensing bag is not optimized due to the spreading out of the bag along the sloped bottom wall and therefore is energy consuming. Secondly, the evacuation of food from the dispensing food bag is relatively poor despite the provision of the sloped geometry for supporting the dispensing bag. Thirdly, the preheating compartment is likely to provide a reduction of the heat-up time but not in a magnitude that can really be considered as a major advantage of the device. Fourthly, the hopper and its preheating compartment is configured to render the positioning and removal of the dispensing bag relatively uneasy in hot conditions because the preheating compartment partly obstructs the passage when the operator needs to have access to the dispensing bag. Fifthly, handling of hot bags in the device may create risks of bums for the operator, in particular when touching hot parts of the hopper.
German company Herman Roelofsen GmbH manufactures food dispensing units comprising a relatively wide box-shaped aluminum container adapted to receive a flexible food bag. The bag is loosely housed within the container and a bar inserted in two slots of the container hangs up the bag to avoid collapsing of the bag within the container. The container fits within a heating metal compartment of the unit which is heated by flexible heating devices. Due to heat loss in the transitions and air gaps from the heaters to the food, the dispensing unit has poor heating performance on large size bags with an heat-up time of more than 10 hours from ambient state for cheese sauce bags. Therefore, microwave preheating of the bag is required before the bag can be installed in the dispensing unit.